
import unittest
import user_code
import ast
import re   
import importlib
import csv
import unittest
import importlib
import pandas as pd
import math

class TestTask(unittest.TestCase):
    def setUp(self):
        self.user_code = importlib.import_module("user_code")

    def test_dataframe_row_count(self):
        importlib.reload(self.user_code)
        df = self.user_code.generate_amortization_schedule(10000, 5, 12)
        _dynamic_test(
            self,
            isinstance(df, pd.DataFrame) and len(df) == 12,
            "DataFrame has correct number of rows for 12 months",
            f"Expected 12 rows, got {len(df) if isinstance(df, pd.DataFrame) else 'not a DataFrame'}",
        )

    def test_monthly_payment_formula(self):
        importlib.reload(self.user_code)
        principal = 5000
        annual_rate = 6
        months = 18
        df = self.user_code.generate_amortization_schedule(principal, annual_rate, months)
        monthly_rate = annual_rate / 12 / 100
        expected_payment = principal * monthly_rate * (1 + monthly_rate) ** months / ((1 + monthly_rate) ** months - 1)
        if isinstance(df, pd.DataFrame) and "Payment" in df.columns:
            payments = df["Payment"].unique()
            _dynamic_test(
                self,
                len(payments) == 1 and math.isclose(payments[0], round(expected_payment, 2), abs_tol=0.01),
                "Monthly payment calculated using amortization formula",
                f"Expected payment: {round(expected_payment,2)}, got: {payments[0] if len(payments) > 0 else 'no payment column'}",
            )
        else:
            _dynamic_test(
                self,
                False,
                "DataFrame has 'Payment' column",
                "DataFrame missing 'Payment' column or not a DataFrame",
            )

    def test_payment_column_consistency(self):
        importlib.reload(self.user_code)
        principal = 8000
        annual_rate = 4.5
        months = 10
        df = self.user_code.generate_amortization_schedule(principal, annual_rate, months)
        monthly_rate = annual_rate / 12 / 100
        expected_payment = principal * monthly_rate * (1 + monthly_rate) ** months / ((1 + monthly_rate) ** months - 1)
        if isinstance(df, pd.DataFrame) and "Payment" in df.columns:
            correct = all(math.isclose(p, round(expected_payment, 2), abs_tol=0.01) for p in df["Payment"])
            _dynamic_test(
                self,
                correct,
                "Each row's 'Payment' column matches computed monthly payment (rounded to two decimals)",
                f"Some payment values do not match expected {round(expected_payment,2)}",
            )
        else:
            _dynamic_test(
                self,
                False,
                "DataFrame has 'Payment' column",
                "DataFrame missing 'Payment' column or not a DataFrame",
            )

    def test_sum_principal_equals_loan(self):
        importlib.reload(self.user_code)
        principal = 15000
        annual_rate = 7
        months = 36
        df = self.user_code.generate_amortization_schedule(principal, annual_rate, months)
        if isinstance(df, pd.DataFrame) and "Principal" in df.columns:
            principal_sum = df["Principal"].sum()
            _dynamic_test(
                self,
                math.isclose(principal_sum, principal, abs_tol=0.1),
                "Sum of all 'Principal' payments equals original principal (within rounding)",
                f"Expected sum {principal}, got {principal_sum}",
            )
        else:
            _dynamic_test(
                self,
                False,
                "DataFrame has 'Principal' column",
                "DataFrame missing 'Principal' column or not a DataFrame",
            )

    def test_final_balance_zero(self):
        importlib.reload(self.user_code)
        principal = 23000
        annual_rate = 3.2
        months = 48
        df = self.user_code.generate_amortization_schedule(principal, annual_rate, months)
        if isinstance(df, pd.DataFrame) and "Remaining Balance" in df.columns:
            last_balance = df["Remaining Balance"].iloc[-1]
            _dynamic_test(
                self,
                abs(last_balance) < 0.1,
                "Last row's 'Remaining Balance' is zero (within rounding)",
                f"Expected 0, got {last_balance}",
            )
        else:
            _dynamic_test(
                self,
                False,
                "DataFrame has 'Remaining Balance' column",
                "DataFrame missing 'Remaining Balance' column or not a DataFrame",
            )

    def test_interest_and_principal_breakdown(self):
        importlib.reload(self.user_code)
        principal = 10000
        annual_rate = 5
        months = 12
        df = self.user_code.generate_amortization_schedule(principal, annual_rate, months)
        monthly_rate = annual_rate / 12 / 100
        if isinstance(df, pd.DataFrame) and all(col in df.columns for col in ["Payment", "Principal", "Interest", "Remaining Balance"]):
            # Test first month breakdown
            interest1 = principal * monthly_rate
            payment = df["Payment"].iloc[0]
            principal1 = payment - interest1
            _dynamic_test(
                self,
                math.isclose(df["Interest"].iloc[0], round(interest1,2), abs_tol=0.01) and math.isclose(df["Principal"].iloc[0], round(principal1,2), abs_tol=0.01),
                "Interest and principal breakdowns are correct for first month",
                f"First month: Expected interest {round(interest1,2)}, principal {round(principal1,2)}; got {df['Interest'].iloc[0]}, {df['Principal'].iloc[0]}",
            )
        else:
            _dynamic_test(
                self,
                False,
                "DataFrame has all required columns",
                "DataFrame missing required columns or not a DataFrame",
            )

def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)

def normalize_text(text):
    text = text.lower()
    text = re.sub(r"\\s{2,}", " ", text)
    text = re.sub(r"\\s*([,:?])\\s*", r"\\1 ", text)
    return text.strip()

def change_var(code: str, var_name: str, value: str) -> str:
    tree = ast.parse(code)
    lines = code.splitlines()
    changed = False
    # Collect all assignment nodes to modify
    assign_nodes = [
        (i, node)
        for i, node in enumerate(tree.body)
        if isinstance(node, ast.Assign)
        and any(isinstance(target, ast.Name) and target.id == var_name for target in node.targets)
    ]

    # If nothing to change, return unmodified code
    if not assign_nodes:
        return code

    # Perform replacements for all matching assignments (from last to first to not break line offsets)
    for i, node in reversed(assign_nodes):
        start_line = node.lineno - 1
        line = lines[start_line]
        indent = ' ' * (len(line) - len(line.lstrip()))
        lines[start_line] = f"{indent}{var_name} = {value}"
        next_line = len(lines)
        for next_node in tree.body[i+1:]:
            if hasattr(next_node, 'lineno'):
                next_line = next_node.lineno - 1
                break
        if next_line > start_line + 1:
            lines[start_line+1:next_line] = []
        changed = True

    return '\\n'.join(lines) if changed else code

if __name__ == "__main__":
    unittest.main()


test_main.py

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Challenge: Generate Amortization Schedule

Solution